As a young brewing apprentice in the early 90s I was lucky enough to visit Frank Boon, a Belgian brewer with his heart set on reviving the tradition of 'lambic' brewing. Rather than adding a pure yeast culture to ferment their beers, Lambic brewers encourage wild yeasts in the atmosphere to do the job instead. I found it fascinating, and have been a little obsessed with unlocking the mysterious secrets ever since. But Frank has spent his entire career mastering this ancient technique (with huge success) and was never going to make my own journey an easy one. It's taken nearly 20 years of conversations and beers with the handful of Lambic brewers and blenders left in production to begin to get an understanding of this dark art. Today I'll share a teaser or two, with you.
Firstly - wild yeasts are all around us, they're in the atmosphere and on plants and fruits and animals and in the soil. They especially love fruit, where they can indulge in the sugar, fermenting it into alcohol. That's how wine is made. They also love the sugar from malted grains, that's how beer is made. In the brewing of regular beer we've long since isolated a single, suitable yeast cell and developed a pure culture from it; in wild fermented beer we encourage as many different wild yeasts as possible to inoculate our sweet wort and ferment it to beer. The thing is, each wild cell will flourish and reproduce under slightly different conditions, and each will create a flavour of its own. This results in a long, slow fermentation and a highly complex finished flavour.
Secondly - in order to achieve balance we need some acidity, and whilst some of the yeast can provide a little (under certain conditions) we really need some friendly bacteria to help us out. A very gentle souring can be obtained by allowing lactobacillus to produce lactic acid, and a sharper acidity, very low in intensity, can be obtained by allowing acetic acid producing bacteria to do their thing.
Thirdly - we need to allow a little oxygen in. In regular beer production we spend a great deal of time excluding oxygen to an obsessively low level, but here, in order to encourage the creation of a little acetic acid, a very slow, controlled ingress of the stuff is required. This is the reason we ferment the beer in oak barrels. We're not after the wood flavour, or the flavour of the liquid that was previously in the barrels, but the ability of the barrel to allow oxygen through the tiny pores in the wood. The pores in the wood also provide a safe harbour for our growing family of wild yeasts, bonus.
Lastly - the acidity of the beer is perfectly suited to, and rather enhanced by, the use of locally grown fruits such as raspberries, cherries, apricots and plums. Not only do these fruits help create elegant and refined beers, they also bring their own wild yeasts to the party, and so each year our family of little helpers grows, becoming ever more complex and nuanced. Double bonus.
Over the last 10 years we've been playing around with oak barrels, local fruits and wild yeasts, randomly 'releasing' our efforts from time to time. Last Saturday we opened a few bottles of a wild apricot beer, sampling it in the weak-but-welcome April sunshine (and a fine afternoon it was too - thanks for all who made it). From today we're beginning to make our efforts available in the webshop and the actual shop and are releasing 'Blend 17' (the original),'Cherry (Disaster) 19' and 'I (still) Dream of Apricots' Over the coming weeks we should have a further three tastings and subsequent releases, starting with a rather pleasingly tart greengage beer. Please come along, and allow me to fill the air with more talk of wild yeasts and mysterious fermentations.